The study of the brain is called neuropsychology and it's a huge topic. Most textbooks will go into much more detail than I will and there are hundreds of helpful websites on brain science. I'm focussing on the core psychology students will need to know for the exam and to make sense of other studies and theories in the Edexcel course.

WHY STUDY BRAINS?

The brain is the seat of consciousness. The brain is where our decisions originate and where processes that lead to our feelings and memories take place. It is where your "self" is located.

The mind is something different. If the brain is a physical organ, the mind is something non-physical: it is the collection of all your thoughts, wishes, memories, feelings and intentions.

Psychology is the study of the mind (the Greek word psyche means "mind") but neuropsychologists are interested in the brain because it seems to shape the mind. We know that changes to the brain produces changes in mental states. We can see this when people take drugs or suffer brain damage, such as from a stroke. Some psychologists argue that the brain is the mind: that all mental states are in fact brain states and once we fully understand the brain we will fully understand the mind, with nothing left over. This is a determinist view, because it claims that the biology of the brain determines all our thoughts.

Other psychologists disagree, saying that it is reductionist to reduce all mental states to brain states. Currently, there seems to be more to the mind than just the brain. For example, the same processes in the brain seem to produce different thoughts or feelings in different people. However, our investigation into the brain is incomplete and we are discovering more about the brain all the time.

The human brain weighs about 3.3 pounds (1.5 kilograms) and makes up about 2% of a human's body weight. It contains about 86 billion nerve cells (neurons) - the "grey matter" - and billions of nerve fibers (axons and dendrites) - the "white matter". These are connected by trillions of connections, or synapses

Brain research used to be limited to examining the dead brains of corpses. This was even less helpful than it sounds, because dead brains liquefy within hours. However, the invention of brain imaging technology has revolutionised our understanding of the brain, because now we can study living brains and "catch them in the act" of thinking or remembering.

Did you know, brain surgery is always done while you're awake and conscious? This is possible because the brain has no pain receptors. The man in the photograph uses a laptop to report what he's feeling as the surgery proceeds. This alerts the surgeon in case he's damaging something that matters!

THE CENTRAL NERVOUS SYSTEM (CNS)

The brain is important, but it doesn't stand all by itself. It works as part of the Central Nervous System (CNS) which includes the nerves running down the spine. The brain and spinal cord together make up the CNS.

Creatures with a CNS are known as vertebrates - a category which includes humans and all other mammals, reptiles, birds and fish, but not (for example) insects or octopodes.

As well as the CNS, you have other nerves in your body. This is the Peripheral Nervous System, which stretches out from your brain and spinal cord into every other part of your body. The Peripheral Nervous System includes sensory nerves (which carry information back to the brain as sensations - the "five senses") and motor nerves (which carry messages from the brain, telling muscles to move and glands to release their hormones).

THE TWO HEMISPHERES

The brain is made up of two similar-looking halves called hemispheres. The two hemispheres are linked by a "bridge" of nerve fibres called the corpus callosum. The corpus callosum allows the left and right hemispheres to communicate with each other.

Yes, the corpus callosum features in the Classic Biological Study by Raine et al. because the murderers in that study showed less activity in the corpus collosum, which suggests their hemispheres weren't communicating properly.

The two hemispheres look identical but the brain is not really symmetrical. This is because the left and right hemispheres specialise in different things. The way different sides of the brain have different functions is called brain lateralisation.

An obvious example of brain lateralisation is that each hemisphere controls a different side of the body. However, it's not as you think: the left hemisphere controls most of the right side of the body, while the right hemisphere controls most of the left side. So if you raise your left hand, that's your right hemisphere controlling the hand.

The two hemispheres have other differences too that are revealed when people suffer brain damage to one side of the brain only (such as a stroke). The brain's language centre is in the left hemisphere and damage to this takes away the power to speak or write (but not to understand language - the right hemisphere can do that). The left hemisphere seems to specialise in reasoning and numbers and more abstract thought; spatial awareness (like reading maps or judging distances) is based in the right hemisphere as is musical ability and artistic creativity.

Left handed people use their right hemisphere to control their writing hand. Over the years, their right hemisphere may pick up some language ability. It's not unusual for left-handers to retain more language ability than right-handers after a stroke that has damaged the left hemisphere.

There's a popular idea that one hemisphere is usually more dominant than the other. This may influence the abilities you are good at and possibly your personality too.

The right-brain looks more fun, in a zany, hippie kind of way. This strikes me as "pop psychology" rather than true science, but if you're interested in identifying your own dominant hemisphere, the test below is a good one:

You don't need to know more than this for the course, but there has been a lot of research into brain lateralisation and the findings are very surprising. For example, in the 1950s Roger Sperry experimented on patients who had undergone brain surgery that cured their epilepsy by separating the two hemispheres of their brains. They were left with two brains instead of one. The results were astonishing.

THE CEREBRAL CORTEX

Human brains have a complex outer layer called the cortex. The cortex handles a lot "higher" brain functions, such as conscious thought and interacting with the world around us. It is divided into a number of areas with different functions, the most important being the four lobes.

In fact there are 8 lobes, because each hemisphere has all four lobes - so there's a left- and a right- version of each of the lobes. As long as your corpus callosum is working properly, the lobe should communicate with its "partner" in the other hemisphere

The frontal lobe handles most of our conscious planning, especially an important part of it called the pre-frontal cortex. Because it is important for self-control and decision-making, it has a big role to play in handling aggression, which is why it was studied by Raine et al. (1997) in the Classic Biological Study. Raine observed murderers showed less activity in the frontal lobe compared to a non-criminal control group.

The ﻿temporal lobe ﻿handles most of our memory functions, which is why it was studied by Schmolck et al. (2002) in the Contemporary Cognitive Study: Schmolck looked at patients who had enormous memory problems because of brain damage to the temporal lobe.

The occipital lobe is at the back of the brain, but it processes sight and our sense of our environment.

The parietal lobe controls language but also specialises in touch and directing bodily movements.

THE LIMBIC SYSTEM

Beneath the cortex is a set of brain structures called the sub-cortical (beneath the cortex) structures. One of the most important of these is the thalamus, which sits at the centre of a group of structures called the limbic system. The limbic system handles memory but also raw appetites and desires - sleep, hunger, aggression and sex. It is thought to be the source of all our basic emotions.

The cerebral cortex is fully developed only in humans. On the other hand, the limbic system is the part of the brain we share with most other animals.

The thalamus is sometimes called "the brain's switchboard", since it handles all the messages coming in from the brain and routes them to where they need to go.

The amygdala is the shape of an almond. It is the brain's "emotion centre". It handles emotional responses to things, especially anger and fear. If it is working properly, we should only fear things that are dangerous. Raine et al. (1997) noticed that the amygdala in murderers functioned erratically; this suggests they might not have felt fear or aggression at appropriate times. Other studies on animals have shown that, when the amygdala is damaged, the animal stops showing fear of threatening stimuli.

The hypothalamus is the shape and size of a pea. It regulates hunger, thirst, sexual arousal and sleep. Animals with damage to the hypothalamus have been known to lose all interest in food or else to start eating compulsively.

The hypothalamus is also part of the endocrine system: it regulates hormone production in the body.

The hippocampus is shaped like a sea horse (it's name means "sea horse"). It is important for forming new memories: it is the brain's "memory factory". Damage to the hippocampus destroys the ability to form new long term memories. A famous example of someone with this problem was H.M. (Henry Molaison), whose hippocampus was removed during brain surgery. Schmolck et al. (2002) found that semantic long term memory was located outside the hippocampus, in the medial temporal lobe.

You'll notice the olfactory bulb is located nearby. This brain structure processes smell. Its link to the limbic system explains how smells can trigger hunger (bacon frying) or sexual arousal (perfume) but also fear (as when animals pick up a threatening scent).

This video covers lots of areas of the brain you don't need to know about, but it's quick and concise and very clear.

THE IMPORTANCE OF NEUROTRANSMITTERSFAST CHEMICAL MESSENGERS

The brain is made up of grey matter which consists of nerve cells called neurons. There are 86 billion of these in your brain. They receive and transmit information in the form of tiny electrical charges.

Motor neurons receive messages from the the CNS and generate movements

Neurons form chains, carrying information to different parts of the brain or spinal cord.

You will need to know the basic structure of a neuron:

Neurons are long stringy things. This shows how three vof them link together, with the axon tips on one neuron nearly touching the dendrites of the next neuron.

The neuron has a cell body with a nucleus in the middle. Round the outside of this are branch-like dendrites (the name comes from the Greek word for "tree") which pick up information from other cells and turn it into an electric signal. This electrical charge travels down the axon, which is the long "tail" of the cell, until it gets to the axon terminals, which look a bit like fingers. These terminals pass the information on to the dendrites of the next cell in the chain. The space between the axon terminal and the dendrite of the next cell is the synaptic gap.

THE SYNAPSE

Electricity cannot "jump" across the synaptic gap, so neurons have a different way of communicating with each other. The axon terminals use the electrical energy to produce chemicals called neurotransmitters. These chemical float across the synaptic gap until they are picked up by special receptors on the dendrite on the other side of the gap. Then they are converted back into an electrical charge which zooms down the next neuron and the process is repeated.

The neurons are like tiny islands separated by seas and the neurotransmitters are boats that travel from one island to the next. Or that's how I like to think of it.

Neurotransmitters that don't attach themselves to a receptor at the other end are recycled to be used again. This is called re-uptake. If reuptake is prevented (inhibited), then the neurotransmitter will stay longer in the synapse, trying to pass on its message. This is how some medicines for depression work: SSRIs (selective serotonin re-uptake inhibitors) boost the amount of the neurotransmitter called serotonin that is active in the brain, improving mood. Prozac (fluorxetine) is a famous SSRI that is prescribed for depression.

Other drugs work by attaching to receptors and "blocking" them so that neurotransmitters cannot attach themselves and get re-uptaken instead.

Re-uptaken. Is that a word?

DIFFERENT TYPES OF NEUROTRANSMITTERS

Neurotransmitters are vital because, without them, neurons could not communicate. There are different neurotranmitters that have different functions. Each neirotranmitter attaches to its own type of receptor on the dendrite and is recycled (re-uptaken) by different chemicals. Here are some examples:

Noradrenaline (also called norepinephrine) produces attention and triggers the "fight or flight response". People with ADHD (attention deficit hyperactivity disorder) seem to benefit from being prescribed noradrenaline

Dopamine is linked to feelings of pleasure and seems to play a part in addiction. Drugs that block dopamine receptors seem to help reduce symptoms in schizophtrenia.

Serotonin is the neurotransmitter for happiness to drugs which boost serotonin (by inhibiting serotonin re-uptake) can reduce depression

Neurotransmitters are fast-acting, taking less than a millisecond to take effect. The speed of neurotransmitters is the speed of thought.

You don't need to know all the neurotransmitters and their structure, but you should be able to name two or three (I recommend serotonin, dopamine and noradrenaline)

By releasing the right "cocktail" of neurotransmitters, your brain cells produce moods and motivations. The right balance of noradrenaline, serotonin and dopamine produces a good mood and clear thinking. Decrease the dopamine and you get anxious; decrease the noradrenaline and you get tired. However, the other neurotransmitters all play a part as well and they interact in very complicated ways.

The balance of neurotransmitters in your brain is affected by your genes, but also by diet, exercise and environment. Alcohol, for example, raises serotonin, but in the long run it lowers serotonin levels.

THE IMPORTANCE OF HORMONESSLOW CHEMICAL MESSENGERS

Neurotransmitters travel tiny distances and take effect in a fraction of a second. Hormones are different. They are carried by your blood all around your body and take effect much more slowly, usually over minutes or hours.

Most hormones are produces by a set of glands in the body called the endocrine system.

You'll notice the hypothalamus that you studied as part of the limbic system is also part of the endocrine system. It has the job of keeping track of hormone production and regulating it.

There are too many hormones to list, but some of the major ones are described below:

The brain's pituitary gland also produces the hormone cortisol, which combats stress and maintains a healthy blood pressure.

Hormones are carried through the body in the blood. When they reach their target cells, they bind to the cell and change its function. Cells respond in particular way to particular hormones. Some hormones reach the brain and bring about mood changes by altering the production or re-uptake of neurostransmitters - for example, testosterone is linked to feelings of aggression.

Hormones can be prescribed as medication:

Oestrogen and progestrogen work as contraceptives

Insulin is used by diabetics

Steroids can treat skin problems and inflammation

APPLYING NEUROPSYCHOLOGY TO REAL LIFEAO2

AGGRESSION

Aggression is linked to different parts of the brain. The amygdala regulates fear and if it is not functioning correctly, then a person may be fearless in dangerous situations but might also engage in aggressive behaviour without fear of the consequences. Thinking about long-term consequences involves the corpus callosum and if this is not working properly then reckless aggression may be more likely. Finally, the pre-frontal cortex (in the frontal lobe) is used for self-restraint, so if this is not functioning well, there will be no "brake" on aggression.

All of these areas of the brain were found to be functioning strangely in the murderers in the Classic Biological study by Raine et al. (1997). Animal studies show that if the amygdala is stimulated with electricity, the animal displays aggressive behaviour.

Changes in neurotransmitters can increase aggression. Dee Higley et al. (1995) studied rhesus monkeys in the wild and found that those who were killed or injured in reckless leaping or fights with older, larger monkeys were more likely to have low serotonin levels (serotonin inhibits aggression).

Hormones such as testosterone have been linked to aggression. A study of prisoners (James Dabbs et al., 1987, 1995) found testosterone levels were higher in those who had been convicted of a violent crime. Those with high testosterone levels were rated higher by other prisoners for being "tough".

Testosterone is linked to "dominance" among animals. It tends to peak in the mating season, when male animals (such as red deer) fight for dominance.

Testosterone has also been shown to peak when human males are single, decline when they get married, and peak again after divorce or separation (Mazur & Booth, 1998).

Some disturbing animal experiments into aggression and the case study of Mark Laribus, whose uncontrollable aggression was linked to a brain tumour near his amygdala

DRUG USE & ABUSE

Recreational drugs (which are taken for pleasure rather than for medical reasons) have an affect on the CNS, which is why they are sometimes called 'psychoactive' drugs. Most of these drugs are illegal, with the exception of so-called "legal highs" that are not yet illegal.

Alcohol is a legal drug that has many effects. It blocks serotinin receptors. Since serotonin calms the brain and inhibits mood, blocking serotonin receptors lifts our mood and makes us uninhibited.

Alcohol is also linked to aggression. Stephanie Gorka et al. (2013) used MRI scans to study activity between the prefrontal cortex (which handles decision making) and the amygdala (which handles emotions). The participants who had taken alcohol showed less brain activity than a control group. This suggests alcohol interferes with the brain's ability to pass information between the emotion centre (the amygdala) and the decision-making centre (the prefrontal cortex).

Nicotine is another legal drug and seems to affect dopamine receptors in a part of the brain called a "reward pathway". The nicotine binds to the receptors the way dopamine would; this excites the neuron, causing an electrical charge to go down the axon to create real dopamine at the next synapse.

Over time, the neurons in the reward pathway start to change, developing fewer dopamine receptors. This is called a hypofunctioning reward system: the brain realises too many dopamine receptors are being stimulated so it starts shutting them down. This reduces your anility to feel rewarded by the drug but also by normal stimuli, like food or sex. The brain needs to produce more dopamine to maintain normal mood states, which is why nicotine is addictive: your brain comes to depend on it to maintain its dopamine levels.

Amphetamines like cocaine are illegal drugs that also involve dopamine in the synapses. However, instead of mimicking dopamine, cocaine shuts down the re-uptake of dopamine. This means the brain's own dopamine stays in the synapse, over-stimulating the dopamine receptors and producing feelings of euphoria (joy). As with nicotine, the long term effects of the drug is desensitisation. The number of dopamine receptors goes down, creating addiction because the brain needs more cocaine to make the reward pathway work.

Cannabis works differently. The drug binds to cannabinoid receptors in various parts of the brain, blocking them so that the neurons don't become excited. There are cannabinoid receptors in the hippocampus, which makes it difficult to form memories when they are blocked. Cannabis also blocks the production of a neurotransmitter called GABA, which "switches off" dopamine production. With less GABA in the reward pathway, there is more dopamine, and hence the "high" associated with the drug.

Excellent 10 minute video which sums up neurotransmitters, drugs and addiction - including addiction to things like gambling

MEMORY & DEMENTIA

Plasticity is the term used to describe how the brain changes each structure in response to stimuli; because the brain is plastic, it can change in response to our experiences, which is how memories are stored.

Dementia is a disease which involves the shrinking of brain tissue. Because different people experience shrinking in different parts of the brain, the early symptoms tend to be different from person to person, but as the damage spreads across the whole brain, sufferers tend to show similar later symptoms.

The hippocampus is a key brain structure for memory formation and the temporal lobe seems to be important for storing and retrieving long term memories. The case of H.M. shows the importance of the hippocampus, because this was the part of the brain removed during H.M.s brain surgery, after which he could no longer create new long term memories. The Cognitive Contemporary Study by Schmolck et al. (2002)shows that the medial temporal lobe (MTL) is important for semantic long term memory and the more damaged this was, the more the patients struggled with semantic LTM.

The hippocampus is needed for retrieval of memories from longer ago. This is why someone in the earlier stages of Alzheimer's may remember childhood memories but not memories from earlier that day.

In Alzheimer's disease (a type of dementia), the amygdala is usually affected later than the hippocampus so the emotional aspects of something may be recalled even if the facts can't be remembered. This may make Alzheimer's sufferers more emotional and illogical.

As the disease damage spreads through the brain, more areas become affected. The cerebral cortex thins (so memories from longer ago are lost) and the brain shrinks. Damage to the left hemisphere is linked to problems with semantic memory and language, so someone may struggle to find the right word for something.

Damage to the visual system in the temporal lobes makes it harder to recognise familiar faces. However, because the pathways for vision and hearing are separate, an Alzheimer's sufferer may still know who a person is once they hear them speak.

As the damage spreads to the frontal lobes, someone with Alzheimer's may struggle with decision-making. More complex tasks, like following a new recipe, often become harder.

However, many abilities are kept, particularly those acquired long ago. Procedural memories such as dancing or playing the piano are mostly stored deep within the brain and these skills often last the longest.

3 minute video gives a step-by-step guide to the progress of Alzheimer's through the brain

Dopamine plays an important role in memory formation. Dopamine is an excitatory neurotransmitter that causes excitement and pleasure but it's real job is to make our brain pay attention to experiences and remember them. Dopamine originally functioned to make us go back to important behaviours (like eating or sex) and stay away from dangerous behaviours (like being chased by bears).

A study by Lifen Zhang et al. (2004) shows that dopamine levels are low in the brains of Alzheimer's sufferers. Medication and diet can be used to slow down the re-uptake of dopamine and this can reduce the symptoms of the disease.

EXEMPLAR ESSAYHow to write a 8-mark answer

An 8-mark “apply” question awards 4 marks for describing brain structure (AO1) and 4 marks for applying it to aggression (AO2). You need a conclusion to get a mark in the top band (7-8 marks).

DescriptionMost human decision making goes on in the frontal lobe of the brain, particularly in the pre-frontal cortex.The brain is divided into two heispheres and the left and right frontal lobes need to communicate wth each other when making decisions. This is done thrugh a bridge of nerves called the corpus callosum.However, instinctve or emotional behaviour comes from a deeper part of the brain called the limbic system.In the limbic system, the amygdala is responsible for processing emotion and making sure we feel appropriate things. In particular, the amygdala handles our fear response.

ApplicationIn a healthy brain, the limbic system would make sure we feel the right emotion (fear or anger) when threatened.The pre-frontal cortex would decide whether to act on this emotion or not. The pre-frontal cortex is able to restrain emoptional reactions.The corpus callosum helps the left and right hemispheres commuicate about decisions. This is important for thinking about long term condsequences.Raine et al. (1997) found that the brains of murderers showed less activity in the pre-frontal cortex and the corpus callosum and unbalanced activity in the amygdala.

ConclusionRaine's findings suggest that brain damage can make peope feel inappropriate aggression or a lack of fear and have difficulty in restraining these feelings or thinking them through. This is backed up by research which shows alcohol interrupts the communication between the amygdala and the pre-frontal cortex.

Notice that for a 8-mark answer you don’t have to include everything about brains. I haven’t mentioned the other parts of the limbic system, testosterone or the hypothalamus. But it is a balanced answer - half description, half application.